# Gearbox torque calculation - input/output

1. Aug 25, 2012

### karl8695

Hi all,

Gearbox output torque driving the input shaft to pump = 0.12348 Nm
Gearbox output speed - 80 rpm
Gearbox input speed - 4 rpm

Gearbox is compound consisting of x4 gears arranged in two pairs -

Gear A, driver = 100 teeth
Gear B, driven = 20 teeth
Gear C, driver = 80 teeth
Gear D, driven = 20 teeth

Gearbox Ratio = 1:20

How do I calculate the input torque?

2. Aug 25, 2012

### huntoon

It seems to me your gearbox is working from low speed to high speed, meaning your gear ratio is speeding up the rotation, which means it is reducing the torque by the same ratio.

take your 'output' torque and multiply this by the ratio to get the input torque.

What's your application? This is opposite of how I use gearboxes.

3. Aug 26, 2012

### karl8695

Hi Huntoon,

The question is related to a concept design where a power spring will be driving the input to a pump; think along the lines of the Baylis wind-up radio.

And thanks for your response, i was hoping it was that simple.

4. Aug 26, 2012

### huntoon

double check your math and my logic. you get what you pay for, you know what I mean.... happy to help though, cheers.